Part of the reason, I think, is that the modern talent extraction system didn't exist then. Think of standardized testing and the education industrial complex as a kind of strip mining operation.

Many of the most capable people are identified before they're adults and then relocated to certain specific institutions, locations, and careers. The result is that the places and subcultures they leave behind fail to thrive in a thousand small ways, the cumulative effects of which are obvious.

In 1900, lots of the people who today are 10x programmers in SF were farmers and small business owners in small towns or rural areas. When you look back at some of the things they figured out and built, you see a level of talent that most of their modern successors lack.